This invention relates to a shim structure for sound dampening brake squeal noise in a disc brake apparatus.
In disc brake apparatus a rotatable rotor rotates with the axle of a wheel to be braked. Two friction pad structures are disposed on opposite sides of the rotor. Each friction pad structure comprises a steel backing and a brake pad. The friction pad structures are moved inwardly, toward one another, under the force supplied by a hydraulically actuated piston and related caliper fingers of a caliper mounting structure. The plates are moved outwardly, away from one another, by return springs.
When the piston and caliper fingers press the backing plates inwardly, the inner surfaces of the braking pads are engaged in frictional, braking contact with the rotor 13.
A relatively high pitched and undesired brake squeal noise can be produced during such braking engagement of the pads on the rotor.
The brake squeal noise is produced by vibration of the friction pad structures during braking actuation.
To reduce and/or to eliminate the undesired brake squeal noise, sound dampening shim constructions have been used, both by original equipment manufacturers and by brake repair shops.
The sound dampening shim constructions have been positioned both between the hydraulically actuated piston and the piston engaging surface of the related steel backing plate and also between the caliper fingers and the caliper contact surface of the related steel backing plate.
Various shim constructions have been used, and examples of certain ones of such shim constructions are referred to in more detail under the Detailed Description of the Preferred Embodiments portion of this application.
The previously used sound dampening shim constructions have had some good features and have had some features which are not so good.
It is a primary object of the present invention to construct a shim structure for sound dampening brake squeal noise which avoids problems presented by prior shim constructions and which has functional and marketing benefits not obtainable with prior shim constructions.